After more than a decade as a star and producer of light romantic comedies, the actress taps her dark side in Grey Gardens.

Three years ago, when Drew Barrymore turned 31, she decided that it was time to test herself. She had made a string of romantic comedies and launched a successful production company whose seven films had generated nearly $900 million in global ticket sales. But Barrymore felt she had grown a little too comfortable for someone “who likes to be out on a limb,” she says. “I thought, Where’s the fear?”

She found more than she bargained for, with two new forays into uncharted terrain. She directed her first feature, Whip It, “a coming-of-self story,” as she calls it, due out later this year. And she signed on to play “Little Edie” Beale in Grey Gardens, airing in April on HBO. Barrymore’s turn as the eccentric, blueblooded cousin of Jacqueline Kennedy Onassis is a mighty departure for the star and producer of the Charlie’s Angels franchise and such romantic romps as 50 First Dates (2004), Music and Lyrics (2007) and this year’s He’s Just Not That Into You. Taking on the dramatic role and stepping behind the camera for the first time were among the most difficult things she has ever done, says Barrymore. “It’s been the years of fears—three straight years of discipline and effort.”

The effort has paid off: Barrymore’s knockout performance in Grey Gardens is likely to win her the kind of acting cred that’s long been associated with the Barrymore family name. Costar Jessica Lange is convinced, she says, that “Drew is going to surprise a lot of people. Little Edie is such a huge role, and people are not accustomed to seeing the depth of Drew’s capacity for drama.”

Barrymore had never fought as hard for a part. “I felt I had more inside of me than I’ve been putting out there,” she says on a hot day in the West Hollywood production offices where she’s editing Whip It. Behind her on a wall, a dry-erase board serves as her calendar, color coded to denote work and personal events (“Ellen/Portia bday party, Arcade Fire@Spaceland, yoga”). At 34, she seems a decade younger, which has as much to do with her go-for-it enthusiasm and candor as it does with her pierced tongue and marigold-yellow painted nails. Petite yet sturdy, she wears ripped boyfriend jeans, black Converse sneakers and electric-blue suspenders over a blue T-shirt. Her fine-boned features, highlighted with eyeliner and nude gloss, are framed by shoulder-length hair, today bright blond with dark roots.

Barrymore hadn’t been on writer-director Michael Sucsy’s short list when he began to cast Grey Gardens. “I understood,” she says, sipping a large bottled ice tea and settling into the sofa. “He thought, She talks like a Valley girl and probably doesn’t have what it takes. I had nothing to prove that I could do this.” She had to plead with Sucsy “to take a chance on me,” she says, and showed up to their meeting carrying a binder thick with annotated Edie research, vowing “to shut out my life and live in the monastery of Edie Beale.” Her determination, says close friend Cameron Diaz, shouldn’t be underestimated: “She has that delicate little jaw, you know? But she’s like a pit bull. You can’t shake her loose.”

A former society beauty who longed to become an actress, Little Edie Beale lived with her mother, Edith Bouvier Beale (played by Lange) in a dilapidated 28-room mansion in East Hampton, overrun with cats and raccoons. The pair were the subject of David and Albert Maysles’s 1975 cult documentary Grey Gardens (and the 2006 Broadway musical), named for the estate where they lived in isolated squalor. The HBO film builds on scenes from the documentary, spanning 40 years and exploring how vibrant Little Edie, her dreams thwarted, came to live out her days with only her overbearing mother as companion.

Playing Edie tapped some private corner of Barrymore’s psyche. Onscreen, and even off, she’s always been eager to please, the sunny, lighthearted star whose winning performance in the 2005 comedy Fever Pitch prompted New York Times critic Manohla Dargis to write that she “inspires more goodwill than any other young actress I can think of working today in American movies.” Such is the range of her appeal that she has claimed the covers of Playboy, Seventeen and Ladies’ Home Journal; this past February, Barrymore beat out Jay Leno and Oprah (Oprah!) to win Greyhound’s first-ever survey to name America’s favorite celebrity road-trip buddy. Barrymore calls herself an optimist but is the first to concede that she works hard to be happy. “I get out of bed with a spring in my step like, I’m going to f—in’ rock this day,” she says. “I’m going to make people happy. Here I go.”

The self-doubting Edie, by turns withdrawn and theatrical, liberated her from playing that part. “I was excited to bring my own pain to something,” says Barrymore, without a hint of any of it. “I mean, contrary to my happy-go-luckiness, I have so much darkness in there. Playing Edie, I felt like s—. I thought, I’m afraid beyond anything I’ve ever known. I’m miserable; I’m scared; I feel sick all the time. And I was like, Good! At least I have somewhere to put it. You know what? I’m not f—in’ happy all the time. I like making people feel good, but it was great not to have to please anybody. I was out there for myself and for her.”

Barrymore stayed in character during the initial rehearsals at the actual Grey Gardens and through the entire seven-and-a-half-week shoot in Toronto in 2007, refusing all contact with even her closest friends, save for her then boyfriend, actor Justin Long, who visited the set once or twice. Being Edie from age 18 to 60 involved wigs, prosthetics and five hours of daily makeup. Wanting to feel as cut off from the world as Edie had, she didn’t use her cell phone or laptop or watch TV, and she read only Edie’s journals and favorite Nathaniel Hawthorne novel, The Marble Faun. The actress insisted that everyone on set call her Edie, and as Edie, composed journal entries and letters to Long on a typewriter. (Her best friend and producing partner, Nancy Juvonen, sent Barrymore a formal letter, addressed to Edie, to invite her to her wedding to Jimmy Fallon.) Fearing she might “snap,” Sucsy recalls, he suggested she return to playing Drew on Saturdays. Her dresser, Kent Cummins, an old friend of hers, confided to Sucsy, “Even the Saturday-night Drew wasn’t the full Drew.”

More complicated was mastering Edie’s idiosyncratic cadences. Barrymore worked with a dialect coach for a year before shooting began, learning to project forward, and not speak out of the right side of her mouth, as is her habit. “She’s always brought so much of herself to her parts,” says Diaz. “This was the first time she was able to leave all of that behind.”

When I mention that her restrictive regimen sounds a lot like being in rehab, she replies quickly, “It’s weird that you bring that up. I got institutionalized as a kid, and I felt like I was back there. A lot of times I found myself unhappy and isolated, and the only other time I felt that way was when I was in there. It was absolutely trying to relearn to live. You are learning to become someone else.” Says Lange, “I don’t think I’ve ever seen an actor accomplish that as completely as Drew did.”

The pair spent most evenings together, sipping wine in each other’s hotel room as they watched dance musicals from the Thirties and smoked cigarettes. “We fell in love. When we’re together, we hold hands and sit really close,” says Barrymore, who appeared to be practically entwined with Lange at the Golden Globes in January. Lange recognizes aspects of Edie in Drew. “For all of her strengths, resilience and tenacity,” Lange says, “there’s also something incredibly tender and vulnerable and childlike about her.”

Barrymore readily saw the parallels—and the differences. “All roads could have definitely led me to being a little bit cloistered and insane,” she says with a laugh, “but I’m not afraid to put it out there, and Edie had a lot of fears that really held her back.”

Each was descended from a storied family, Edie from the Bouviers and Drew from one of the most famous acting clans in American theater. (Grandfather John Barrymore, great-aunt Ethel and great-uncle Lionel Barrymore all died before she was born.) And each was tied to a controlling mother, whose own stage ambitions had gone unrealized. Drew’s mother, Jaid, a struggling actress, raised her in Hollywood. Drew made her first commercial at 11 months and had already done two TV movies when Steven Spielberg cast her, at age six, in the 1982 megahit E.T. Overnight she was the “hot tot,” as People dubbed her, and the youngest person ever to host Saturday Night Live. “I feel like I came out of the womb and was punted—there you go, out in the world!” she says. The family breadwinner at age seven, she was soon the wild child, spending her days on movie sets and nights clubbing with her mother. She had her first drink when she was nine, and by 13 was in rehab; her best-selling memoir, Little Girl Lost, published when she was 14, is a cautionary tale of parental neglect, forfeited childhood, and cocaine and alcohol abuse—and then recovery—that should have been required reading for Britney and Lindsay.

When I ask if she sees her mother, Barrymore gives the only terse answer in the interview. “No contact,” she replies. Her father, John, an alcoholic actor, left before Drew was born and was absent for much of her childhood, though they forged a bond when he was dying of bone-marrow cancer, and Barrymore, then 29, paid for his care. “He was so feeble, I could actually nail him down,” she says sardonically. “He was such a flighty bird—unattainable and off doing his own thing. I’m sure it’s affected my relationships with men. I’m sure I’m sadder about it than I admit, but I accept that a lot easier than my mother’s and my relationship, which is more tumultuous.”

While her father didn’t offer any apologies, she brightly recalls a moment when they were sitting together in his room and he suddenly looked down at her bare feet. “Ah, you were made perfectly,” he told her. “And I was like, ‘This was worth hanging out with you for,’” she says.

Despite the almost parasitic nature of the Beales’ relationship, Barrymore sees theirs as a “love story” and calls her relationship with her own mother “the polar opposite.” “My mother and I split ways when I was very young and have never really reconciled,” says Barrymore, who has lived on her own since she legally emancipated herself at age 15. “Edie chose her mother over the world.”

Barrymore has since built her own family, a tight circle of friends she calls her “tribe,” whose members include Diaz, Juvonen and Chris Miller, vice president of Flower Films, her production company. “They’re the glue. They’re everything to me,” she says. Barrymore and Diaz met as teenagers, at the Beverly Hills soda shop where they both hung out. “I was a model then, and she was—Drew Barrymore!” says Diaz, recalling that her friend was just out of rehab “and trying to get herself back together. She was so funny and sweet. Drew is always Drew. She’s never changed.”

Naturally gregarious, Barrymore is as likely to invite 12 people over to play Cranium at her home in West Hollywood as she is to organize a trip to Mexico or hit a club to catch the latest band. “She knows every single band out there,” says Diaz. And she is never without a plan. “Nothing makes her happier,” says Juvonen. “It comes from the uncertainty of her growing up with ‘I don’t know where I’m going to live or where my mom is.’ It makes her feel safe. The man who really steals her heart will be a planner.”

When the two met in 1994, Juvonen had zero experience in the film business. Then 27, she was working as saxophonist Clarence Clemons’s assistant when the 19-year-old Barrymore dared her to move to Los Angeles to produce movies. “Drew Barrymore and romantic comedy weren’t synonymous then,” she says, pointing out that the actress, who had just posed nude for a Playboy spread and played teen temptress Amy Fisher in a made-for-TV movie, was in need of a different direction. “She wasn’t an A-lister.” Together they mapped out a course, launching Flower in 1995. “I always had faith that all of Drew’s guardian angels would see her through the worst of it,” says Spielberg, by e-mail.

Barrymore’s voice catches with emotion as she talks about Juvonen. “Here’s the part where I lose it,” she says. “Nan’s the love of my life.” Both big sister and sounding board, Juvonen is a pragmatist who isn’t afraid to dole out tough love. Barrymore has unending energy, she notes, and a “compulsive” work ethic to go with it. “Drew’s not casual at all,” Juvonen says. “She gets hyperworried and intense about things.”

Whip It, their 10th film together, cost about $12 million and was filmed in just 10 weeks. Before agreeing to let the perpetually tardy Barrymore direct, however, Juvonen insisted that she learn to be on time. “For years I said, ‘You need to show me you can do this,’” Juvonen recalls. “She had no parents; no one said to her, ‘These things matter.’” As the director, says Juvonen, Barrymore had to learn how to “step in as the leader, and not as the famous person who everyone says yes to. And, boy, did she ever.”

Whip It is about a 17-year-old girl (played by Ellen Page) breaking free from her mother’s small-town values to find her place as part of a roller derby team. To Barrymore, who costars as derby girl Smashley Simpson, it’s about “finding your tribe,” and another mother-daughter love story with personal resonance. An avid photographer and cine­phile, she included images opposite every page of the script to help the actors and crew understand the “tone” she was after. (The references run from William Eggleston and a rabid Old Yeller to Martin Scorsese’s Alice Doesn’t Live Here Anymore.)

Her first lessons in directing came from Spielberg, on the set of E.T. She remembers giving him a story she’d written about a mother and daughter that he later nicknamed “Terms of Endrewment.” “Drew and I were like dad and daughter, and this was four years before I had any children of my own,” says Spielberg, who became her godfather. On his set she discovered, briefly, the structure and familial ties missing at home. “I came to the profound understanding that I had found my place,” she says of her first “tribe.” “So I wasn’t going to let it go for anything in the world. For me it was survival.”

Recently Spielberg gave her notes after she showed him a rough cut of “my first child,” as she refers to Whip It. “I don’t want to sell out the moment because it’s so personal and private,” she says, suddenly drawing a line. “It was very emotional for me. I was like, ‘This is who I became because of your guidance.’” Spielberg considers the film a self-assured debut. “I was not surprised that she knew exactly where to put the camera,” he says, “because at six years old she was telling me where she thought I should put the camera.”

Barrymore has made 40 movies since then, and when she says, “I have red carpet tonight,” it’s with the nonchalance of a camper announcing that she has kickball after lunch. The occasion is the premiere of He’s Just Not That Into You, featuring a clutch of stars, among them Barrymore, Jennifer Aniston and Scarlett Johansson. Barrymore plays a woman who can’t get a date, though offscreen, her romantic life is one of the most chronicled in the world. (DREW BARRYMORE SAYS TONGUE RING SCARES OFF MEN screamed a headline after she dished on Ellen in February.) “She loves being in love and talking about it,” says Juvonen. “She’s like, ‘Can you believe it? He touched my hair!’”

Barrymore has been married twice—for eight weeks to bar owner Jeremy Thomas in 1994, and for five months to comedian Tom Green in 2001. For five years, until 2007, she went out with New York rocker Fabrizio Moretti of the Strokes, which was “one of the most, if not the most, important relationships I’ve had in my life,” says the actress. “We’re still very close. I’m just learning who I am and how relationships work and how to make them function. No different from anyone else.”

For her next project, Barrymore will produce How to Be Single, based on the chick-lit novel of the same name. And she has been single herself since last June, when she split with Long, another He’s Just Not That Into You costar, though at the premiere they embraced warmly on the red carpet, to the delight of the paparazzi. Looking chic in a strapless Lanvin cocktail dress, her hair pulled back into a glamorous fall, she seemed utterly at home. While the other stars went through their paces—Ben Affleck, for one, dutifully posed for pictures, then powered to the end of the line, ignoring press entreaties of “Ben! Please! Just a wave?”—Barrymore breezily chatted up reporters, even circling back to take questions from those she overlooked.

If, in her romantic life, Barrymore is still finding her way, professionally she’s clearly arrived. The challenges of the past three years have convinced even her of that. “I’m finally like, I can do these things,” she says. “Now I can start to experience more joy and not be so worried all the time—that would be a really important liberation for me.”